I know a diver who parks his SIB this way when overnighting at a hotel (presumably to really drain it out. As I recall, he has some lumber stands that are inserted while someone hold the trailer nose up.
FWIW, it is a good idea to store a trailer boat with the keel sloped to the rear and the drain plug removed; accumulated rain water can overload the trailer. Though the pic is a little overkill in this regard.
jky
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